In the manufacture of semiconductors and integrated circuits, various films or layers of materials are deposited during the fabrication of such circuits. Dielectric films are widely deposited on semiconductor wafers to electrically isolate conductive layers and enable useful interconnects between such layers. Dielectric and other films, such as hydrides, are often formed by chemical vapor deposition (CVD). The CVD process deposits a material on a surface by transport and reaction of certain gaseous precursors on the surface. CVD reactors come in many forms. Low pressure CVD systems (LPCVD) and atmospheric pressure CVD systems (APCVD) operate on thermal CVD principles. Plasma may be employed to assist decomposition of chemicals for reaction in plasma enhanced CVD systems (PECVD).
Since CVD deposits the components of the precursor chemicals, it is important to minimize contaminants in the CVD reactor environment because such contaminants may become deposited in the film. Contaminants in the film damage the function of the devices on the wafer and reduce the device yields. Metal contamination is especially detrimental to dielectric layers formed on silicon wafers because the metal impurities will exhibit electrical properties after thermal processing thereby affecting gate oxides and other device features.
Contaminants can arise from many sources. In addition to the presence of impurities in the precursor chemicals, contaminants can arise from the CVD systems themselves. CVD processing apparatus are comprised of a variety of metal components and are a potential source of metal contamination. During semiconductor processing metal atom contaminants may arise from some of the metal components making up the processing equipment. Such contaminants may be delivered to the semiconductor substrates where they contaminate the substrate surfaces and/or deposit in the film. Accordingly, it is desirable to provide a method for reducing metal contamination from metal surfaces in semiconductor processing equipment and for depositing films with low metal contamination.